The present invention relates to a method and an apparatus for determining acceptability of a press contact terminal by predicting contact loads between press contact blades and a core wire when an electric wire is inserted between the press contact blades or the like.
Various electronic apparatus are mounted on an automobile as a vehicle. The automobile is wired with a wire harness for transmitting a predetermined power and signal to the electronic apparatus. The wire harness is provided with a plurality of electric wires and connectors attached to end portions of the electric wires.
The electric wire includes a conductive core wire and an insulating sheath portion for covering the core wire. The connector is provided with a terminal metal piece attached to the electric wire and a connector housing containing the terminal metal piece. The terminal metal piece is made of a conductive drawn sheet or the like. The terminal metal piece is electrically connected to the core wire of the electric wire. The connector housing is made of an insulating synthetic resin and formed in a box-like shape.
The wire harness having the above-described constitution transmits a predetermined power and signal to respective electronic apparatus by coupling to wire the connector with a connector provided at the above-described electronic apparatus.
There is a case of using a press contact terminal as a terminal metal piece of the wire harness. The press contact terminal is provided with a bottom wall for positioning the core wire of the electric wire on a surface thereof, a pair of side walls erected from opposite edges of the bottom wall and press contact blades extended from respectives of the pair of side walls in directions of approaching each other. The press contact terminal is inserted with the electric wire between the press contact blades. Then, the press contact blades are brought into contact with the core wire by cutting the sheath portion. In this way, the press contact terminals are electrically connected to the electric wire, that is, brought into press contact with the electric wire. The press contact terminals are attached to the connector housing.
At this occasion, there is a case in which when the electric wire is inserted between the press contact blades, an interval between the pair of side walls of the press contact terminals is expanded after having been brought into press contact therewith. Therefore, when the electric wire is inserted between the press contact blades, the press contact blades are brought into contact with the core wire by cutting the sheath portion and therefore, in inserting the electric wire between the press contact blades, a load in a direction of hampering the insertion is generated. Therefore, in a press contact apparatus or the like for inserting the electric wire between the press contact blades, the electric wire is inserted between the press contact blades by a force exceeding the load.
When the load is excessively increased, it is conceivable that the press contact terminal is abnormally deformed or chipped off. In a state of attaching the press contact terminal to the connector housing, it is conceivable that the connector housing is destructed.
Therefore, in developing the press contact terminal, a designed press contact terminal is trially produced, the electric wire is actually inserted between the press contact blades and the load and the expansion of the interval between the side walls are measured. A relationship between the load and the expansion of the interval between the side walls is calculated and acceptability of design of the press contact terminal is determined based on the relationship.
A the time of a mass production after completing the design, the press contact terminal is brought into press contact with the electric wire and contained in the connector housing to constitute the wire harness. In order to maintain/improve quality of the wire harness, even in the case of the press contact terminal in mass production, it is desired to calculate the relationship between the expansion of the interval between the side walls and the load in bringing the electric wire into press contact therewith. It is desired to determine acceptability of the press contact terminal based on the relationship.
The loads are based on contact loads between the core wire and the press contact blades. Various measuring apparatus (refer to, for example, Patent Reference 1) have been proposed to measure the loads, that is, the contact loads.
The measuring apparatus is provided with strain gage type load cells (hereinafter, referred to as load cells) on outer sides of respectives of the pair of side walls of the trially produced press contact terminal. Front ends of the load cells are brought into contact with outer faces of the side walls of the press contact terminal before press contact. The measuring apparatus measures the contact loads by inserting the electric wire between the press contact blades and measuring loads applied on the load cells.
Patent Reference 1
JP-A-2001-183251
In an actual press contact terminal, when an electric wire is inserted between press contact blades, a pair of side walls are separated from each other. However, in the measuring apparatus, the front ends of the load cells are brought into contact with the outer faces of the side walls and therefore, even when the electric wire is inserted between the press contact blades, the pair of side walls are made to be difficult to separate from each other. Therefore, the loads applied on the load cells tend to be larger than the contact loads between the press contact blades and the core wire of the actual press contact terminal.
Therefore, when the measuring apparatus of the related art is used, the contact loads between the press contact blades and the core wire cannot accurately be measured. When the measuring apparatus of the related art is used, the side walls are made to be difficult to separate from each other and therefore, it is naturally difficult to accurately measure the expansion of the interval between the side walls. Therefore, when the measuring apparatus having the load cells is used, not only the contact loads between the press contact blades and the core wire cannot accurately be measure but also the expansion of the pair of side walls, that is, the expansion of the press contact blades cannot accurately be measured. Therefore, when the measuring apparatus provided with the load cells is used, it is difficult to accurately determine acceptability of the press contact terminal.
On the other hand, when the press contact terminals are brought into press contact with the electric wire, since the electric wire is press fit between the press contact blades, an interval between the pair of side walls of the press contact terminal may be widened.
It is conceivable that when the interval between the pair of side walls is excessively expanded, the press contact terminal is abnormally deformed or chipped off. It is conceivable that in a state in which the press contact terminal is attached to the connector housing, the connector housing is destructed.
Therefore, in developing the press contact terminal, a designed press contact terminal is trially produced, the electric wire is actually press fit between the press contact blades and expansion of the interval between the pair of side walls is measured. In order to measure expansion of the interval between the pair of side walls of the press contact terminal, there is proposed a measuring method for measuring expansion of the interval between the pair of side walls by measuring respective displacements of the pair of side walls by using, for example a laser displacement meter (refer to, for example, Patent Reference 2).
According to the measuring method, a pair of the laser displacement meters are provided. A displacement of one of the side walls is measured by irradiating laser to one of the side walls by one of the laser displacement meters. A displacement of other of the side walls is measured by irradiating laser to other of the side walls by other of the laser displacement meters. In this way, according to the measuring method, expansion of the interval between the pair of side walls is measured.
Patent Reference 2
JP-A-2001-159514
An angle made by a surface of the bottom wall and a surface of the side wall is changed before press contact and after press contact, that is, the side walls are inclined by bringing the electric wire into press contact therewith. Therefore, according to the measuring method described in the publication, a portion of the side wall on which laser impinges is shifted before press contact and after press contact. Therefore, it is conceivable that the laser displacement meter cannot accurately measure the displacement of the side wall. An incident angle and an emitting angle of laser relative to the side wall is changed before contact and after contact and therefore, it is conceivable that the laser displacement meter cannot measure the displacement of the side wall further accurately.